[PATCH 2/4] PCI/AER: Clamp negative ratelimit burst to zero

[Yazen Ghannam]

The correctable and nonfatal "_ratelimit_burst" attributes store
whatever kstrtoint() parses, so a negative value lands directly in
ratelimit_state.burst.

___ratelimit() reads a negative burst as an uninitialized
ratelimit_state and gives a WARNing.

Clamp negative values to zero and document the clamping behavior.

Fixes: b4fe7398def6 ("PCI/AER: Add sysfs attributes for log ratelimits")
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-pci/20260714191826.BA81E1F000E9@xxxxxxxxxxxxxxx/
Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
---
 .../ABI/testing/sysfs-bus-pci-devices-aer     | 21 ++++++++++++-------
 drivers/pci/pcie/aer.c                        |  3 +++
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-pci-devices-aer b/Documentation/ABI/testing/sysfs-bus-pci-devices-aer
index 5ed284523956..215cf8bd4c30 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci-devices-aer
+++ b/Documentation/ABI/testing/sysfs-bus-pci-devices-aer
@@ -130,9 +130,10 @@ What:		/sys/bus/pci/devices/<dev>/aer/correctable_ratelimit_interval_ms
 Date:		May 2025
 KernelVersion:	6.16.0
 Contact:	linux-pci@xxxxxxxxxxxxxxx
-Description:	Writing 0 disables AER correctable error log ratelimiting.
-		Writing a positive value sets the ratelimit interval in ms.
-		Default is DEFAULT_RATELIMIT_INTERVAL (5000 ms).
+Description:	Writing 0, or any negative value, disables AER correctable
+		error log ratelimiting. Writing a positive value sets the
+		ratelimit interval in ms. Default is
+		DEFAULT_RATELIMIT_INTERVAL (5000 ms).
 
 What:		/sys/bus/pci/devices/<dev>/aer/correctable_ratelimit_burst
 Date:		May 2025
@@ -143,14 +144,17 @@ Description:	Ratelimit burst for correctable error logs. Writing a value
 		before ratelimiting. Reading gets the current ratelimit
 		burst. Default is DEFAULT_RATELIMIT_BURST (10).
 
+		Writing 0, or any negative value, suppresses all logs
+		unless the interval attribute is also 0.
+
 What:		/sys/bus/pci/devices/<dev>/aer/nonfatal_ratelimit_interval_ms
 Date:		May 2025
 KernelVersion:	6.16.0
 Contact:	linux-pci@xxxxxxxxxxxxxxx
-Description:	Writing 0 disables AER non-fatal uncorrectable error log
-		ratelimiting. Writing a positive value sets the ratelimit
-		interval in ms. Default is DEFAULT_RATELIMIT_INTERVAL
-		(5000 ms).
+Description:	Writing 0, or any negative value, disables AER non-fatal
+		uncorrectable error log ratelimiting. Writing a positive
+		value sets the ratelimit interval in ms. Default is
+		DEFAULT_RATELIMIT_INTERVAL (5000 ms).
 
 What:		/sys/bus/pci/devices/<dev>/aer/nonfatal_ratelimit_burst
 Date:		May 2025
@@ -161,3 +165,6 @@ Description:	Ratelimit burst for non-fatal uncorrectable error logs.
 		allowed per interval before ratelimiting. Reading gets the
 		current ratelimit burst. Default is DEFAULT_RATELIMIT_BURST
 		(10).
+
+		Writing 0, or any negative value, suppresses all logs
+		unless the interval attribute is also 0.
diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index 6f2460231422..401cd3a1b3d0 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -752,6 +752,9 @@ const struct attribute_group aer_stats_attr_group = {
 		if (kstrtoint(buf, 0, &burst) < 0)			\
 			return -EINVAL;					\
 									\
+		if (burst < 0)						\
+			burst = 0;					\
+									\
 		pdev->aer_info->ratelimit.burst = burst;		\
 									\
 		return count;						\
-- 
2.55.0